In a continuous web inkjet printer, some print jobs include duplex printing of forms. As used herein, the term “form” refers to a section of a larger print medium, such as a media web, that is identified by a pre-existing form indicator mark or feature. For example, top-of-form (TOF) indicators can include marks that are arranged at predetermined intervals along the length of the media web to delineate individual forms in the media web. The indicator marks are inscribed on the media web prior to the media web roll being mounted in the printer and passed through the printer. Other indicators include holes that extend through the media web at predetermined intervals. During a printing operation, the printer registers individual printed pages with the form indicators to produce printed images that are registered with the predetermined boundaries of the forms on the media web. In some embodiments, the media web includes pre-printed text or images in each form page, and the printing engine forms printed images that are superimposed on the pre-printed markings. In duplex printing, two print engines in one or more printers print images onto opposing sides of individual forms on the print medium. These images on opposing sides are registered with the form indicators on each side of the media and with each other in the process direction. After completion of the printing process, the web is separated along the boundaries between forms to produce individual duplex printed forms.
Existing printing systems perform duplex form printing by timing the operation of printheads or other marking units to form images on each side of the forms with reference to the pre-existing form indicator marks or features. In some duplex printers, however, the media web can experience deformation or slip in the media path within the printer. Either or both of the deformation and slip can introduce registration errors for printed forms that the existing methods for registration based on only on form indicator location fail to correct. Thus, improvements to methods for registration of printed images on the first side and second side of a form would be beneficial.